Network traffic is always unpredictable and the only basic assurance that can be offered is the best effort traffic delivery. To overcome this challenge, Quality of Service (QoS) is applied throughout the network. This ensures that network traffic is prioritized according to specified criteria and receives preferential treatments.
QoS enables you to assign various grades of network service to different types of traffic, such as multi-media, video, protocol-specific, time critical, and file-backup traffic. To set up the priority of packets in the Managed Switch, click the folder QoS Priority Configuration from the Switch Configuration menu and then four options within this folder will be displayed.
1. QoS Port Configuration: To set up each port‟s QoS default class, QCL, Priority, Queuing Mode, Queue Weighted.
2. QoS Control List: To create, edit or delete QCL settings.
3. QoS Rate Limiters: To configure each port‟s Policer and Shaper Rate.
4. Storm Control: To enable or disable Unicast, Broadcast and Multicast Storm Control.
4.4.8.1 QoS Port Configuration
Select the option QoS Port configuration from the QoS Configuration menu and then the following screen page appears.
Configure Default Class:
Click the pull-down menu to choose the class level “Low”, “Normal”, “Medium” or “High”.
The default class level of each port is “Low”.
Configure QCL:
A QCL number is assigned to each port based on the information in the QCL table. Please refer to QoS Control List for QCL settings.
Configure User Priority:
There are eight priority levels that you can choose to classify data packets. Choose one of the listed options from the pull-down menu for CoS (Class of Service) priority tag values.
The default value is “0”.
The default 802.1p settings are shown in the following table:
Priority Level Normal Low Low Normal Medium Medium High High
802.1p Value 0 1 2 3 4 5 6 7
Configure Queuing Mode:
There are two different queuing modes:
Strict:This indicates that services to the egress queues are offered in the sequential order and all traffic with higher priority queues are transmitted first before lower priority queues are serviced.
Weight: Weighted Round-Robin shares bandwidth at the egress ports by using scheduling weights 1, 2, 4, 8 for queues 1 through 4 respectively.
Configure Queuing Weighted:
Click the pull-down menu to select values of Queue weighted for each port.
4.4.8.2 QoS Control List
The following screen page appears if you choose QoS Priority Configuration and then select QoS Control List.
QCL: Select a QCL number (1~24).
QCE Type: View-only field that shows QCL‟s current QCE type.
Type Value: View-only field that shows QCL‟s current type value.
Traffic Class: View-only field that shows QCL‟s Traffic Class.
Click New to add a new QCL setting and then the following screen page appears.
Click Edit to view and edit registered QCL settings.
Click Delete to remove a current QCL setting.
Current/Total/Max List: View-only field.
Current: This shows the number of current registered QCL setting(s).
Total: This shows the number of total registered QCL setting(s).
Max List: The shows the number of maximum QCL settings that are available for registration. The default number is 12.
QCE Type: Click the pull-down menu to select the desired privilege for the QCE type operation.
Ethernet Type: When you choose Ethernet Type as your preferred QCE Type, you can further specify your Ethernet Type in this field, such as 88A8, 9100, 9200, 9300.
VLAN ID: When you choose VLAN ID as your preferred QCE Type, you can further specify VLAND ID value from 1 to 4094.
TCP/UDP Port: When you choose UDP/TCP Port as your preferred QCE Type, you can further specify TCP/UDP Port by selecting “Specific” or “Range” from the pull-down menu.
“Specific” allows you to assign “TCP/UDP Port No.”. On the other hand, “Range” allows you to assign TCP/UDP port range in “TCP/UDP Port Range” field.
DSCP: When you choose DSCP as your preferred QCE Type, you can further specify DSCP value.
Traffic Class: When you choose Ethernet Type, VLAN ID, UDP/TCP Port or DSCP as your preferred QCE Type, you can further specify traffic class queues. Four types of Traffic Class you can choose from are “Low”, “Normal”, “Medium” and “High”.
Priority Class: When you choose ToS or Tag Priority as your preferred QCE Type, you can assign a priority level (Low, Normal, Medium or High) to the specific priority class.
4.4.8.3 QoS Rate Limiter
Select the option QoS Rate Limiter from the QoS Priority Configuration menu and then the following screen page appears.
Configure Policer Rate:
This allows users to specify each port‟s inbound bandwidth. The excess traffic will be dropped. Specifying “0” is to disable this function.
Configure Shaper Rate:
This allows users to specify each port‟s outbound bandwidth. The excess traffic will be dropped. Specifying “0” is to disable this function.
4.4.8.4 Storm Control
Select the option Storm Control from the QoS Priority Configuration menu to set up the broadcast storm control parameters for ports and then the following screen page appears.
When a device on the network is malfunctioning or application programs are not well designed or properly configured, broadcast storms may occur that will degrade network performance and even cause a complete halt. The network can be protected from broadcast storms by setting a threshold for broadcast traffic for each port. Any broadcast packets exceeding the specified threshold will then be dropped.
Three options of frame traffic are provided to allow users to enable or disable the storm control.
Unknown Unicast Rate: Enable or disable unknown unicast storm control and set up unknown unicast rate.
Multicast Rate: Enable or disable multicast storm control and set up multicast rate.
Broadcast Rate: Enable or disable broadcast storm control and set up broadcast rate.
Limitation: When broadcast storm control is enabled and the connected interface and CPU belong to the same VLAN, the broadcast rate will be set to 4K even though the other rate option is selected.